Turbo Steve
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- Jan 11, 2000
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So, How Often Should I Change My TDI's Engine Oil?
Let me start out by saying that "you can never change your engine oil too frequently!" The more you do it as needed, the longer the engine will last.
The whole debate about exactly "when you change your oil" is somewhat of a grey area. Manufacturers tell you every "7,500 / 10,000 miles" or so. Your neighbor with a classic or luxury car tells you every 3,000 miles. Your other friend who drives a truck tells you he's "never once changed the oil."
The bottom line here, is: large quantities of water are produced by the normal combustion process of diesels, and, depending on engine wear, some of it gets into the crank case. If you have a good crankcase breathing system, the water is removed or burned off. Even so, in cold weather a lot of condensation will take place.
This is bad enough in itself, since water is not noted for its lubrication qualities in an engine. Even worse, water disolves any nitrates formed during the combustion process and leaves you with a mixture of Nitric (HNO3) and / or Nitrous (HNO2) acid circulating round your engine! So not only do you suffer a high rate of wear at start-up and when the engine is cold, you suffer a high rate of subsequent corrosion during normal running or even when stationary.
The point I'm trying to make is that the optimum time for changing oil ought to be related to a number of factors, of which distance traveled or time on the hour meter is probably one of the least important in most cases.
Consider, for example, my selection in rough order, the areas of greater importance:
1 - Number of Cold Starts and city versus highway driving (can produce more condensation and acidic buildup in a cold engine)
2 - Outside Temperature (how long before the TDI engine warms up enough to stop serious condensation)
3 - Effectiveness of Crankcase Ventilation System (e.g. PCV)
4 - Condition / Wear of the TDI Engine (excessive piston blow-by multiplies this problem)
5 - Efficiecy of Fuel Injectors and Quality of Fuel (a clean spray pattern can create less soot)
6 - Distance Traveled or Time on an Engine Hour Meter
The first three items should be given equal top billing or weighting. They need to be taken together since a given number of "cold" starts in the hot summer are not the same as an equal number conducted in cold January. The effect in either case will be modifed by how much "blowby" gets past the pistons.
What we are really after here folks is the severity and duration of the initial condensation period. All other things being equal, that will tell you how much condensation / acid is probably being produced in your crankcase.
More than anything else, these key six areas should also provide a good guideline to follow, for matching oil & filter change intervals to your own "unique style of driving."
Example, we know that VW "recommends" changing the oil in a TDI engine every 10,000 miles. Most people forget or haven't noticed that this is for "NORMAL Conditions." Jon Bartlett's type of highway driving is a perfect example of operating under "Normal Conditions."
Obviously, 90% of us do not fall into that same category and need to be reminded that VW recommends "more frequent oil changes ... [for] SEVERE Conditions," one of which is described by them as "short trips or operating under extremely low temperatures."
I suggest that we consider evaluating our percentage of city versus highway driving (taking into account the number of cold starts) and then outside ambient temperature, in order to establish or estimate how long we can go before changing our diesel's oil.
Obviously, the quality of oil comes into the picture here (another story
), but this should not be as important as confirming your own "unique plan" (frequency of oil changes) through oil analysis on an occasional basis.
[This message has been edited by Turbo Steve (edited February 11, 2000).]
Let me start out by saying that "you can never change your engine oil too frequently!" The more you do it as needed, the longer the engine will last.
The whole debate about exactly "when you change your oil" is somewhat of a grey area. Manufacturers tell you every "7,500 / 10,000 miles" or so. Your neighbor with a classic or luxury car tells you every 3,000 miles. Your other friend who drives a truck tells you he's "never once changed the oil."
The bottom line here, is: large quantities of water are produced by the normal combustion process of diesels, and, depending on engine wear, some of it gets into the crank case. If you have a good crankcase breathing system, the water is removed or burned off. Even so, in cold weather a lot of condensation will take place.
This is bad enough in itself, since water is not noted for its lubrication qualities in an engine. Even worse, water disolves any nitrates formed during the combustion process and leaves you with a mixture of Nitric (HNO3) and / or Nitrous (HNO2) acid circulating round your engine! So not only do you suffer a high rate of wear at start-up and when the engine is cold, you suffer a high rate of subsequent corrosion during normal running or even when stationary.
The point I'm trying to make is that the optimum time for changing oil ought to be related to a number of factors, of which distance traveled or time on the hour meter is probably one of the least important in most cases.
Consider, for example, my selection in rough order, the areas of greater importance:
1 - Number of Cold Starts and city versus highway driving (can produce more condensation and acidic buildup in a cold engine)
2 - Outside Temperature (how long before the TDI engine warms up enough to stop serious condensation)
3 - Effectiveness of Crankcase Ventilation System (e.g. PCV)
4 - Condition / Wear of the TDI Engine (excessive piston blow-by multiplies this problem)
5 - Efficiecy of Fuel Injectors and Quality of Fuel (a clean spray pattern can create less soot)
6 - Distance Traveled or Time on an Engine Hour Meter
The first three items should be given equal top billing or weighting. They need to be taken together since a given number of "cold" starts in the hot summer are not the same as an equal number conducted in cold January. The effect in either case will be modifed by how much "blowby" gets past the pistons.
What we are really after here folks is the severity and duration of the initial condensation period. All other things being equal, that will tell you how much condensation / acid is probably being produced in your crankcase.
More than anything else, these key six areas should also provide a good guideline to follow, for matching oil & filter change intervals to your own "unique style of driving."
Example, we know that VW "recommends" changing the oil in a TDI engine every 10,000 miles. Most people forget or haven't noticed that this is for "NORMAL Conditions." Jon Bartlett's type of highway driving is a perfect example of operating under "Normal Conditions."
Obviously, 90% of us do not fall into that same category and need to be reminded that VW recommends "more frequent oil changes ... [for] SEVERE Conditions," one of which is described by them as "short trips or operating under extremely low temperatures."
I suggest that we consider evaluating our percentage of city versus highway driving (taking into account the number of cold starts) and then outside ambient temperature, in order to establish or estimate how long we can go before changing our diesel's oil.
Obviously, the quality of oil comes into the picture here (another story
[This message has been edited by Turbo Steve (edited February 11, 2000).]